Experimental and Scale-span Numerical Investigations in Conventional and Longitudinal Torsional Coupled Rotary Ultrasonic Assisted Drilling of CFRPs

Abstract

Longitudinal torsional coupled rotary ultrasonic assisted drilling (LTC-RUAD) technology is introduced to improve the surface roughness of the hole wall and solve the tear, burr and delamination of carbon fiber reinforced polymers (CFRPs) induced by large thrust force and torque during conventional drilling (CD). An experiment and scale-span numerical investigation of drilling CFRPs was presented for both CD and LTC-RUAD process in this study. A drilling experimental platform using LTC-RUAD was built via a novel independently designed and manufactured LTC-RUAD vibration actuator, while the drilling experiments involving T700S-12K/YP-H26 CFRPs specimens with different process parameters were carried out by adopting the different ultrasonic vibration amplitude (UVA) in the longitudinal and torsional directions. Then, a three-dimensional (3D) scale-span FE simulation model of CD and LTC-RUAD which applied the different UVA using tapered drill-reamer (TDR) are developed to find more details about the effects of machining quality of the holes. Experimental and simulation results revealed that the maximum average thrust force reduction is observed to be as high as 30% under certain drilling conditions, and the maximum average thrust force and the delamination factor of the drilled hole shows a "concave" trend with the increase of the UVA. The quality at the exit of the drilled hole is the best when adopting Sr=2000rpm, Sf=0.01mm/rev, Alon=7.02μm and Ator=9.29μm in LTC-RUAD. The delamination factor is only 0.054. The damage factors are reduced by 69.67% compared with CD.